It is common for an owner of a vehicle, such as an automobile, truck or the like, to tow or trail various trailers, such as a camper trailer, a boat trailer, a storage trailer, or the like. Electrical power is made available to the trailer by means of an electrical wire connector electrically connected to the towing vehicle's electrical supply system. Vehicle electrical connectors can be made to accommodate connection between the various trailers and the vehicle. For example, the Society of Automotive Engineers (SAE) has promulgated a standardized connection scheme that allows for intermixed connection between various types of vehicles and trailers.
In some vehicles, a standardized connection scheme includes an output for providing current to an auxiliary power source such as a battery of the trailer. When the trailer is connected to the vehicle, a vehicle battery charges the trailer battery via the output of the electrical connector. When charged, the trailer battery supplies power to various electrical loads of the trailer. In many cases, trailers have brakes that assist the vehicle's brakes when stopping. In addition, when a break-away switch near a trailer hitch is opened (i.e. when the trailer becomes detached from the hitch) the trailer brakes will engage to stop the trailer. Many of these trailers rely on the trailer battery to provide power to the brakes in the event of the break-away. However, in some instances, the battery voltage may be insufficient to provide stopping power due to a lack of charge. Current methods of recognizing a lack of charge may include manually testing the battery before departure. Such methods are rarely performed by a vehicle owner before each departure.